The Clinical and Educational Core (CEC;Core 2) will assume Center-wide responsibility for four major components of the ExCITRA (P20), including: 1) the recruitment, screening, diagnostic assessment, and clinical care of all human research participants;2) the comprehensive neurocognitive assessment of all subjects successfully meeting eligibility criteria;3) the concurrent psychopharmacologic characterization of individuals'subjective, behavioral, and neurocognitive responses to stimulant self-administration (cocaine in cocaine dependent subjects) and/or administration (methylphenidate in cocaine dependent and healthy control subjects);and, 4) the coordination of research career development of affiliated trainees in the interdisciplinary and translational neurobiology of drug addicfion.